PHGY 210 Lecture Notes - Lecture 11: Atrioventricular Node, Pacemaker Current, Pacemaker Potential
25 Feb 2013
School
Department
Course
Professor
Document Summary
Lead: either the physical piece of wire attached to the patient, or the final result of differentials. Put 0 to the minus lead of the voltmeter, which then allows for a reading of just the limbs. 12 leads are taken since they are all different. Each of the leads is looking at the activity of the heart from different angles. The right arm unipolar lead would have an inverted t wave. Action potentials: the ventricular muscles have much longer action potentials, lasting nearly 300ms. Since k+ is high in the side at rest, the nernst potential for k+ is dominant for the cell at rest. When activated, na+ floods the cell, and the nernst potential pushes towards the na+ potential. The ina+ fast inward na+ current follows as the permeability for sodium dramatically increases when activated. While this is happening, the permeability of k+ drops. Calcium acts as a chemical signal to spread the signal around.
